How small is the Earth

[St Landrew]

On a completely different but related in as much as its-to-do-with-physics-and-that's-what-makes-stars-work point......

 

Consider a scale model of an atom constructed on a football pitch:

 

If the nucleus is a football in the middle of the centre circle, the electrons would be peas orbiting outside the edge of the pitch.

 

It really is remarkable we don't fall through the floor considering that most of matter is nothing.

 

Physics, astronomy and various other sciences are truly mind boggling, awe-inspiring and wonderful. It's a crying shame that our children aren't taught them properly.

 

Echo that sentiment. We had the most boring Physics teahcer it was possible to have. However, we did have that rare commodity - a decent Geography teacher.

[skintsaint]

Is that further than Newcastle?

 

 

Imagine the petrol costs!

[Saint in Paradise]

Sorry MB but as you like to post "Hot Pics" I win because my picture of the Earth is

"hotter" than the very dark image you posted.:D:D

[Master Bates]

Sorry MB but as you like to post "Hot Pics" I win because my picture of the Earth is

"hotter" than the very dark image you posted.:D:D

 

Mine was Earth in the future, it's a bleak future i'm afraid.

[scott_saints]

I hate space. It's far too confusing!!

 

And how the f**k can something go on forever?!!!

 

Woah, I need to stop thinking like this it's only morning!

[saintwarwick]

Is that further than Newcastle?

 

Depends what route you take.

[Durleyfos]

This thread makes me feel

 

I'm going to buy myself 'Physics for Dummies' next time I'm in Waterstones.

[keithd]

This thread makes me feel

 

I'm going to buy myself 'Physics for Dummies' next time I'm in Waterstones.

 

save yourself threpence and read this fred. its got everything an information hungry man might need.......

[Saint in Paradise]

I find the "Big Bang" start of the Universe difficult to understand.I cannot understand

how an explosion could create something from nothing, Also what caused this explosion

of nothing ?

I again find it difficult to understand how so much stuff could be created from nothing

bearing in mind that there are billions of Galaxys how could they just appear from nothing ?

Finally if they were created from a Big Bang what created the creator of this Bang ?

[Master Bates]

I find the "Big Bang" start of the Universe difficult to understand.I cannot understand

how an explosion could create something from nothing, Also what caused this explosion

of nothing ?

I again find it difficult to understand how so much stuff could be created from nothing

bearing in mind that there are billions of Galaxys how could they just appear from nothing ?

Finally if they were created from a Big Bang what created the creator of this Bang ?

 

The Big Bang theory depends on two major assumptions, the universality of physical laws, and the Cosmological Principle. The cosmological principle states that on large scales the universe is homogeneous and isotropic.

 

These ideas were initially taken as postulates, but today there are efforts to test each of them. For example, the first assumption has been tested by observations showing that largest possible deviation of the fine structure constant over much of the age of the universe is of order 10−5. Also, General Relativity has passed stringent tests on the scale of the solar system and binary stars while extrapolation to cosmological scales has been validated by the empirical successes of various aspects of the Big Bang theory.

 

If the large-scale universe appears isotropic as viewed from Earth, the cosmological principle can be derived from the simpler Copernican Principle, which states that there is no preferred (or special) observer or vantage point. To this end, the cosmological principle has been confirmed to a level of 10−5 via observations of the CMB. The universe has been measured to be homogeneous on the largest scales at the 10% level.

[Saint in Paradise]

And I thought I was confused before :D I don't understand a word of that

[Guest Dark Sotonic Mills]

And I thought I was confused before :D I don't understand a word of that

 

Nor does Bates...

 

In fact I believe he used a random word generator there.

[Guest Hacienda]

It is a fact, however, that by measuring the doppler and blue light shift, that the evidence exists that the universe is expanding from a central point.

[Master Bates]

And I thought I was confused before :D I don't understand a word of that

 

No what you wanted?

 

Nor does Bates...

 

In fact I believe he used a random word generator there.

 

[Master Bates]

It is a fact, however, that by measuring the doppler and blue light shift, that the evidence exists that the universe is expanding from a central point.

 

Either we are at the center of an explosion of galaxies—which is untenable given the Copernican Principle—or the universe is uniformly expanding everywhere. This universal expansion was predicted from general relativity by Alexander Friedman in 1922 and Georges Lemaître in 1927, well before Hubble made his 1929 analysis and observations, and it remains the cornerstone of the Big Bang theory as developed by Friedmann, Lemaître, Robertson and Walker.

 

The theory requires the relation v = HD to hold at all times, where D is the proper distance, v = dD / dt, and v, H, and D all vary as the universe expands (hence we write H0 to denote the present-day Hubble "constant"). For distances much smaller than the size of the observable universe, the Hubble redshift can be thought of as the Doppler shift corresponding to the recession velocity v. However, the redshift is not a true Doppler shift, but rather the result of the expansion of the universe between the time the light was emitted and the time that it was detected.

 

That space is undergoing metric expansion is shown by direct observational evidence of the Cosmological Principle and the Copernican Principle, which together with Hubble's law have no other explanation. Astronomical redshifts are extremely isotropic and homogenous, supporting the Cosmological Principle that the universe looks the same in all directions, along with much other evidence. If the redshifts were the result of an explosion from a center distant from us, they would not be so similar in different directions.

 

Measurements of the effects of the cosmic microwave background radiation on the dynamics of distant astrophysical systems in 2000 proved the Copernican Principle, that the Earth is not in a central position, on a cosmological scale. Radiation from the Big Bang was demonstrably warmer at earlier times throughout the universe. Uniform cooling of the cosmic microwave background over billions of years is explainable only if the universe is experiencing a metric expansion, and excludes the possibility that we are near the unique center of an explosion.

[Guest Hacienda]

Either we are at the center of an explosion of galaxies—which is untenable given the Copernican Principle—or the universe is uniformly expanding everywhere. This universal expansion was predicted from general relativity by Alexander Friedman in 1922 and Georges Lemaître in 1927, well before Hubble made his 1929 analysis and observations, and it remains the cornerstone of the Big Bang theory as developed by Friedmann, Lemaître, Robertson and Walker.

 

The theory requires the relation v = HD to hold at all times, where D is the proper distance, v = dD / dt, and v, H, and D all vary as the universe expands (hence we write H0 to denote the present-day Hubble "constant"). For distances much smaller than the size of the observable universe, the Hubble redshift can be thought of as the Doppler shift corresponding to the recession velocity v. However, the redshift is not a true Doppler shift, but rather the result of the expansion of the universe between the time the light was emitted and the time that it was detected.

 

That space is undergoing metric expansion is shown by direct observational evidence of the Cosmological Principle and the Copernican Principle, which together with Hubble's law have no other explanation. Astronomical redshifts are extremely isotropic and homogenous, supporting the Cosmological Principle that the universe looks the same in all directions, along with much other evidence. If the redshifts were the result of an explosion from a center distant from us, they would not be so similar in different directions.

 

Measurements of the effects of the cosmic microwave background radiation on the dynamics of distant astrophysical systems in 2000 proved the Copernican Principle, that the Earth is not in a central position, on a cosmological scale. Radiation from the Big Bang was demonstrably warmer at earlier times throughout the universe. Uniform cooling of the cosmic microwave background over billions of years is explainable only if the universe is experiencing a metric expansion, and excludes the possibility that we are near the unique center of an explosion.

 

I never said WE were close to the centre, rather that there is expansion from a relatively central point.

 

The fact that the universe is moving, as measured by Doppler and relight shift is undeniable. It is what is causing that is where the debate centres.

[Saint_clark]

I never said WE were close to the centre, rather that there is expansion from a relatively central point.

 

The fact that the universe is moving, as measured by Doppler and relight shift is undeniable. It is what is causing that is where the debate centres.

 

I think it's being held on the back of four elephants who are standing on the shell of a turtle, and it is that which causes the universe to move.

[Master Bates]

[Saint in Paradise]

Hubble is in more trouble

 

http://spaceflightnow.com/shuttle/sts125/081017hubble/

[dubai_phil]

Sorry MB but you're posts are just WAY too simplistic. I think the Turtles and elephants could be closer to the mark.

 

I'm alright with this expanding universe stuff, but what about the Dark does it Matter? and other critically important questions.

 

So then I read stuff and see - ha MB's wrong.... there are more opinions about all of this than there are people at fault for the mess at SMS

 

http://www.telegraph.co.uk/digitallife/main.jhtml?xml=/connected/2002/04/30/ecftime30.xml

 

COSMOLOGISTS have come up with a new model of the universe in which time does not begin or end but turns in a never ending cycle, as suggested by some ancient philosophies and religions.

 

 

Modern society believes that time is linear, stretching from today back to the birth of the universe in the Big Bang of creation some 15 billion years ago. But, inspired by the movements of the Sun and heavens, some ancient cultures saw time as being cyclic, so that events and lives would endlessly repeat.

 

Now, two leading cosmologists suggest something similar to this eternal return in a new model of the universe where time has no beginning or end. Instead, the cosmos undergoes cycles of expansion and contraction so that it endlessly dies and rises from its ashes.

 

The conventional model of the universe starts with the Big Bang, followed by a short period of extremely fast expansion and cooling, called inflation, which accounts for many features of the universe today. But this model does not account for recent discoveries by astronomers, notably of the way the expansion of the universe seems to have been accelerated by a mysterious force called "dark energy".

 

In the current issue of the journal Science, a new model of the universe is put forward by Profs Paul Steinhardt of Princeton University and Neil Turok of Cambridge University that may replace the role of inflation with a new chain of events and account for this dark energy - rather than add it in an ad hoc way.

 

The new idea is an extension of what is called the "ekpyrotic theory", based upon the mathematical framework of M theory (the current favourite contender for a theory of everything) which describes the birth of our universe in the collision of enormous four-dimensional membranes, or branes. Two infinite branes - our own universe and a "mirror universe" - live a tiny fraction of a metre apart. "If you wait long enough, the branes approach one another," said Prof Steinhardt. They collide, and the energy of that collision creates all the matter and energy in our universe.

 

The membranes "bounce" and separate again. The newborn universe, on its brane, then evolves and eventually burns out.

 

The theorists were surprised to realise that the collapse-and-bounce cycle repeats itself ad infinitum.

 

Each cycle begins with a Big Bang, in which radiation and matter are generated. The universe expands and cools over trillions of years, becoming dominated by the dark energy that accelerates the expansion of the universe until the matter and radiation become dilute. Then dark energy decays, causing the next Big Bang to occur.

 

Prof Turok explained that each cycle would be identical in broad outline - the density and rate of expansion of the universe - though would differ in detail. "Different galaxies and stars would form each time round, through amplification of random density variations which are generated near the end of each cycle (when the dark energy is decaying)."

 

To accommodate the branes, the universe proposed in the new model has more than the four dimensions - three of space and one of time - that we are familiar with. It is in one of these additional dimensions, the universe begins to contract, ending in a Big Crunch so that the cycle begins again.

 

"The period of contraction is quite unlike what we normally think of, a contraction of our usual dimensions," said Prof Steinhardt. "It is a contraction, bounce and re-expansion of an extra dimension."

 

The model sounds obscure but accounts for dark energy and overcomes a problem encountered by earlier cyclic models of the cosmos in coping with the second law of thermodynamics - where a quantity linked with disorder (called entropy) always increases, to provide an arrow of time, from low to high entropy.

 

While the Big Bang starts out as a dot consisting of a homogeneous soup of particles and energy, the Big Crunch collapses all the detritus of a cosmos into a point: in other words, the Crunch has much more entropy than the Bang. Thus, when the universe begins to expand once again, it starts off with much more entropy (disorder) and this changes the cycle time. "The problem is that, going back in time, the duration of these cycles shrinks to zero and you are back to the idea of having a beginning," said Prof Steinhardt.

 

Each part of the new model's cycle, in which dark energy causes the universe to accelerate, also causes the entropy from the previous cycle to be diluted. In this way, entropy does not have to be taken into account.

 

Will the new theory catch on? Only time will tell. The team has started to propose experiments to see if its model is correct - cosmologists do not care how crazy their ideas sound, only if they are mathematically consistent and can account for the features of our cosmos.

 

If the model is confirmed, questions about the beginning of time would be meaningless, said Prof Steinhardt. "Rather the universe has been cycling forever. That's quite fascinating and one of the reasons why a cyclic universe has been an appealing notion since time immemorial."

[Saint in Paradise]

"While the Big Bang starts out as a dot consisting of a homogeneous soup of particles and energy"

 

Ok so how could something so small create so many trillions of stars etc ?

 

What created this small dot ?

 

:confused:

[Master Bates]

"While the Big Bang starts out as a dot consisting of a homogeneous soup of particles and energy"

 

Ok so how could something so small create so many trillions of stars etc ?

 

What created this small dot ?

 

:confused:

 

By the sounds of things OXO.

[Crouchie's Lawyer]

I too have a telescope and I too have seen the craters on the moon and the rings of Saturn.

 

Can I ask Jilleh, are there craters on uranus?

 

Do you think its quite hot on those stars, I mean, would I get swetty on pollux?

[St Landrew]

"While the Big Bang starts out as a dot consisting of a homogeneous soup of particles and energy"

 

Ok so how could something so small create so many trillions of stars etc ?

 

What created this small dot ?

 

:confused:

 

Aha, you've very quickly hit on the weakness of the Big Bang theory. It's reckoned that all time started with the Big Bang. Scientists talk about fundamental gases that coalesced before the Big Bang. Oops, did I say before..? Isn't that not allowed if the celestial clock isn't ticking..?

 

Science twists and turns to make things fit in convenient boxes when it is unsure or even unknowing about how things work. Once there were Fixed Stars and the Universe revolved around the Earth, and scientists were as sure of those truths as we are of our truths today. For my money, the Big Bang theory has a lot going for it, but let's not think for more than one moment that it is the whole answer. I believe there are physical laws in the universe as yet undiscovered which explains how it came to be. IMO, we're just too unaware and unimaginative to contemplate what they are at present. The data isn't in. Scientists talk a lot about the mass of the universe, and how big it is, and what shape it is. But that is to define barriers to it. And if that is the case, what's on the other side..? :confused:

 

http://en.wikipedia.org/wiki/Big_bang

[Marsdinho]

Bates - since when were you a space geek!

 

 

Since Google was invented

Edited 25 October, 2008 by Marsdinho

[Saintandy666]

Why were the planets scared of Jupier?

 

Because Jupiter Saturn Uranus.

 

 

Harrrrr harrrrrr

[EastleighSoulBoy]

Aha, you've very quickly hit on the weakness of the Big Bang theory. It's reckoned that all time started with the Big Bang. Scientists talk about fundamental gases that coalesced before the Big Bang. Oops, did I say before..? Isn't that not allowed if the celestial clock isn't ticking..?

 

Science twists and turns to make things fit in convenient boxes when it is unsure or even unknowing about how things work. Once there were Fixed Stars and the Universe revolved around the Earth, and scientists were as sure of those truths as we are of our truths today. For my money, the Big Bang theory has a lot going for it, but let's not think for more than one moment that it is the whole answer. I believe there are physical laws in the universe as yet undiscovered which explains how it came to be. IMO, we're just too unaware and unimaginative to contemplate what they are at present. The data isn't in. Scientists talk a lot about the mass of the universe, and how big it is, and what shape it is. But that is to define barriers to it. And if that is the case, what's on the other side..? :confused:

 

http://en.wikipedia.org/wiki/Big_bang

 

I have a fondness for this thought process:

 

What if we actually live on protons/electrons/other as yet undiscovered particles of an atom which are part of a chair leg/whatever on a greater plane?

 

I don't mean this as a joke but to provoke further thought/comment.

 

BTW This thread is really one of the most serious but fun to read!

[Saint in Paradise]

Many,many,many years ago I read a short cartoon SF story about a prophet

who said his world was doomed. He said his world would be

destroyed by a great flood. The last 2 pictures were of the planet

being flooded and a lab technician washing a microscope slide

[dubai_phil]

I have a fondness for this thought process:

 

What if we actually live on protons/electrons/other as yet undiscovered particles of an atom which are part of a chair leg/whatever on a greater plane?

 

I don't mean this as a joke but to provoke further thought/comment.

 

BTW This thread is really one of the most serious but fun to read!

 

OMG somebody else holds the same weird idea that I have....

 

After all it's as likely as absolutely nothing suddenly deciding to explode

 

(Sort of a Men in Black necklace on the cat type of thingy)

[Redbul]