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Why is red shift alone not enough to support the Big Bang?

An exam question that I am currently struggling on, any help? (please read the question carefully)

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It doesn't prove that it's expanding, and it says mothing about it being finite. All you know is that it's moving away, which could be for any reason.

CMBR (must have originated from a fixed point) and Olber's Paradox (must be finitely old) help with that.

Hope this helps :smile:

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(edited 9 years ago)
Original post by KingsIheuks97
An exam question that I am currently struggling on, any help? (please read the question carefully)


Well, it proves that galaxies are moving away. We can also prove that the furthest galaxies are moving away the fastest which is evidence for expansion but it doesn't prove the theory that the universe was once constricted :smile:

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Reply 3
Red Shift doesn't helps to support the Big Bang as the Red Shift states galaxies are only moving away, so there's no evidence nor proof. CMBR & Olber's Paradox helps to give evidence, but not proof. If it's proven, it becomes a law.
(edited 9 years ago)
Reply 4
If that's the actual wording of the question then that's disgraceful. "Redshift happens when light or other electromagnetic radiation from an object is increased in wavelength, or shifted to the red end of the spectrum. In general, whether or not the radiation is within the visible spectrum, "redder" means an increase in wavelength equivalent to a lower frequency and a lower photon energy, in accordance with, respectively, the wave and quantum theories of light." (from Wikipedia). Cosmological redshift or Hubble's Law should have been stated.

Regardless, there are plenty of things it doesn't explain: aboundance of He, CMB (sort of), etc.


Original post by AlphaNick
It only suggests that all galaxies are moving away from each other - that the universe is expanding. It doesn't necessarily suggest that everything originated from one point in space... but CMBR can support that theory.


That's exactly what Cosmological redshift suggests...
(edited 9 years ago)
Reply 5
Original post by AlphaNick
Bare in mind that this is GCSE stage... we hardly have to know anything about it...


You just told the OP something that is comletely incorrect. Obviously the fact that all galaxies (on a macro scale) are moving away from each other suggests that at some point in the past everything existed in the same place.
Reply 6
Original post by JAIYEKO
Red Shift doesn't helps to support the Big Bang as the Red Shift states galaxies are only moving away, so there's no evidence nor proof. CMBR & Olber's Paradox helps to give evidence, but not proof. If it's proven, it becomes a law.


No it doesn't. :s-smilie: That doesn't make any sense - a law is a single, observable, testable statement, like Newton's laws.
(edited 9 years ago)
Original post by JAIYEKO
Red Shift doesn't helps to support the Big Bang as the Red Shift states galaxies are only moving away, so there's no evidence nor proof. CMBR & Olber's Paradox helps to give evidence, but not proof. If it's proven, it becomes a law.


It's scientifically impossible to prove something to be true. Even laws can be disproven, they're just something that we've seen to be extremely likely based on empirical evidence.

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Reply 8
Original post by AlphaNick
Incorrect or not, that's what we're taught at GCSE.


No, it wasn't. You were not explicitly told that Cosmological redshift does not suggest everything in the Unvierse originated from the same point. If you were then your teacher is an idiot.
That's not the only thing that supports the big bang theory, you have to consider background microwave background radiation also.
Original post by majmuh24
It doesn't prove that it's expanding, and it says mothing about it being finite. All you know is that it's moving away, which could be for any reason.

CMBR (must have originated from a fixed point) and Olber's Paradox (must be finitely old) help with that.

Hope this helps :smile:

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The big bang theory doesnt point to a finite universe tho. If anything, the universe is infinite

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Reply 11
Original post by CJKay
No it doesn't. :s-smilie: That doesn't make any sense - a law is a single, observable, testable statement, like Newton's laws.

Ok, prove that Newton's law is incorrect pls...
Reply 12
Original post by JAIYEKO
Ok, prove that Newton's law is incorrect pls...


Newton's laws are only approximately correct.
Original post by QuantumSuicide
The big bang theory doesnt point to a finite universe tho. If anything, the universe is infinite

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What makes you think that? At the very least, Olber's paradox suggests that it's finitely old.
(edited 9 years ago)
Original post by JAIYEKO
Red Shift doesn't helps to support the Big Bang as the Red Shift states galaxies are only moving away, so there's no evidence nor proof. CMBR & Olber's Paradox helps to give evidence, but not proof. If it's proven, it becomes a law.

You do know what a scientific law is, right?
If the redshift of galaxies was proportional to their distance then presumably this WOULD prove the big bang theory would it not? Since running this backwards it would imply that everything originated from a single point.


Maybe the question means that "Big Bang" only refers to if the Universe began at a singularity. Whereas alternate theories such as the Universe is oscillating are compatible with these observations


Or perhaps there definition of the Big Bang only requires the Universe started from a hot dense state in which case you would also need to detect the background radiation "afterglow" from the Big Bang.



TBH the question is ambiguous at best.


Or is this question in the religious studies course and they require the answer: "Actually God created the Universe"
(edited 9 years ago)
Let's keep the argument out of this thread, guys.

Original post by KingsIheuks97
An exam question that I am currently struggling on, any help? (please read the question carefully)


Hey OP, I've just moved your thread to the physics forum where you're more likely to get answers. :smile:
expansion isn't enough to prove a big bang.
The great rival to big bang theory was steady state theory which happily accommodated redshift and expansion but held that the universe had always existed and constantly created new matter everywhere as it expanded.
steady state theory didn't begin to run into any fatal contradictory evidence until the 1960s
Original post by majmuh24
What makes you think that? At the very least, Olber's paradox suggests that it's finitely old.


It's most likely infinite. All scientific experiments regarding the shape of the universe suggest an infinite universe. The universe can still be infinite despite having a finite age.

http://wmap.gsfc.nasa.gov/universe/uni_shape.html

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(edited 9 years ago)
Reply 19
Original post by QuantumSuicide
It's most likely infinite. All scientific experiments regarding the shape of the universe suggest an infinite universe. The universe can still be infinite despite having a finite age.

http://wmap.gsfc.nasa.gov/universe/uni_shape.html

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How does that work? The universe starts from one point (Big Bang Singularity) and expands at some velocity (I'm aware that its accelerating, but imagine its constant ok?) This means that at any finite time later, the universe will have expanded a finite amount from an initial finite position. Therefore, the universe cannot be infinite in terms of size.

Bubble Universes and multiverse theories do allow for infinite sizes probably, but they don't refer to the universe (in terms of The Big Bang Theory anyway).

I don't understand that site's point tbh... it seems to suggest that space is everywhere and the universe is expanding into it, which isn't true.

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