a question to einstein fans?

Question

the cosmological constant which is said to be right recently has brought me into confusion. einstein had used it in his equations so that they give a solution of stable universe and later had also admitted this as his greatest mistake.this being the case how could cosmological constant be right.

i know everything about it. i just want to know how it became right .How did they prove it right and based on what concept did they do that

Answer 1

Einstein introduced the cosmological constant so his equations would allow a static (rather than an expanding) universe. When it was found that the universe does expand, Einstein called it a mistake and dropped it in his further research. The size of the constant that Einstein needed for a static universe is not the same as that needed to account for the accelerating expansion that we actually see. Essentially, Einstein needed one value and the actual value is different.

Answer 2

I agree with campbelp2, mathemetician and iridflare.

I'd like to point out a couple additional things:

1) We have no idea what the Dark Energy actually is. It seems fairly certain that something is causing an acceleration of the expansion of the Universe (based on supernova data and microwave background data). That something is called Dark Energy, for the sake of having a name for it.

2) Einstein's cosmological constant, capital Lambda, is a linear term that can be put into the gravitational source equations of General Relativity without affecting them very much---it has no effect except on the very largest scales, and so has no consequences outside of cosmology. You can add in a small value of Lamba to the equations and it makes no difference to black holes, pulsar orbits, or any of the other tests of General Relativity. This constant has the same effect as the Dark Energy, provided the equation of state parameter of the dark energy, w, is constant in time with a value of -1. This may or may not be true, and there are several experiments currently underway to determine if it is true. If w is not constant, the Dark Energy could be some other unknown force. In any case, there is no explanation as to why Lambda should have the small but non-zero value it would have to have in order to be the Dark Energy.

This is at the forefront of current physics research, and basically we don't know much. One thing we really don't know is why the various forces of physics (electricity, magetism, strong force, weak force, gravity and possibly Dark Energy) exist with the strengths they do and not other forces, or if there are additional unknown forces we don't know about. This may be tied up by string theory, but don't hold your breath.

Answer 3

Einsteins cosmological constant is correct as long as you are describing a stable universe that isn't expanding.

Since he didn't know that the universe was expanding, it turned out to be a mistake.

Answer 4

I agree with mathematician, except for the last sentence (which I may have misunderstood) - "Essentially, Einstein needed one value and the actual value is different."

The cosmological constant has been identified with vacuum energy, and when dark energy was first discovered it was thought that they might be the same thing. It turns out that there's too much vacuum energy, by many orders of magnitude, so dark energy must be something different. It's not that Einstein got the value wrong, he wasn't describing the same thing.

Answer 5

Einstein thought the constant was just a fudge factor to explain why the universe is NOT expanding. Shortly after that, Edwin Hubble discovered that the universe IS expanding, which prompted Einstein to make his statement.

Answer 6

something just flew over my head

Answer 7

umm....i think i will answer some beauty questions instead!