How is this possible?? OK... i guess the universe is expanding faster than the speed of light and really is 78 billion light years in size, but the farthest we could possibly see would be light from galaxies 13 billion light years away.... am i right?
somebody explain this please.
somebody explain this please.
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General theory of relativity. Really too complicated to fully explain but I will try. because of the speed the objects are travelling relative to us the distance they have travelled is actually shorter for them. So, as wierd as it sounds, those objects that are 78 billion light years apart have actually travelled less than 13 billion light years. Read a book on quantum physics it gets wierder than that. I especially like the particles that behave differently depending on whether or not you're watching.
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Actually, the observable universe is about 46.5 billion light years in radius, which corresponds to 93 billion light years in diameter. Furthermore, the Universe as a whole is known to be at least a thousand times that big.
The expansion of the Universe does not go at a constant 'speed' measured in m/s or some equivalent. Rather, it has a speed per distance, which corresponds to units of s^-1, or Hz. Moreover, that measurement itself is gradually changing, and it may have been changing far faster in the distant past, immediately after the Big Bang. We can see objects that appear farther away than 13.7 billion light years because the space between us and them has been expanding in the meantime, while the light was still traveling.
The expansion of the Universe does not go at a constant 'speed' measured in m/s or some equivalent. Rather, it has a speed per distance, which corresponds to units of s^-1, or Hz. Moreover, that measurement itself is gradually changing, and it may have been changing far faster in the distant past, immediately after the Big Bang. We can see objects that appear farther away than 13.7 billion light years because the space between us and them has been expanding in the meantime, while the light was still traveling.
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Easy, you just need a little maths.
It is not some hypothetical boundary that is moving outwards. Every volume of space that is not sufficiently bound by gravity is expanding. Therefore the expansion is cumulative.
Do the maths. If you have a field that is 100 metres across and each square metre expands at 1 metre per hour then after one hour the field will NOT be 1 metre larger. It will be 100 metres larger!
It is not some hypothetical boundary that is moving outwards. Every volume of space that is not sufficiently bound by gravity is expanding. Therefore the expansion is cumulative.
Do the maths. If you have a field that is 100 metres across and each square metre expands at 1 metre per hour then after one hour the field will NOT be 1 metre larger. It will be 100 metres larger!
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