How can we know that background microwave radiation is a truly cosmic phenomenon and not local to us?

Question

I apologise if this is a daft question but it would be nice to know given backround radiation is seen as proof for a big bang.

Answer 1

Not a 'daft' question at all..! In fact I'd never wondered about what you've asked so some research was called for. Here's what I came up with --

The temperature of the CMBR is uniform to better than one part in a thousand! This uniformity is one compelling reason to interpret the radiation as remnant heat from the Big Bang; it would be very difficult to imagine a local source of radiation that was this uniform. In fact, many scientists have tried to devise alternative explanations for the source of this radiation but none have succeeded.

Also, cosmologists have carefully computed what the initial temperature at the instant of the Big Bang must have been. We also have a good idea of when the Big Bang cooked off. Knowing the initial temperature and the age of the universe, the current temperature of the CMBR is consistent with both.

Answer 2

If the background radiation were local, it would show larger concentrations close to matter local to us. It's not limited to our solar system or galaxy which means it comes from a long long distance away.

Answer 3

We know this as space is technically a perfect vacuum and therefore should have a temperature of Absolute Zero - but it does not.

The average temperature in space in our solar system is ~3.2 Kelvin (3.2 degrees above absolute zero)

This must come from somwhere and that is the microwave radiation you are talking about.

Answer 4

You can't lick your elbow.

Dude, Radiation comes from the sun, and our sun isn't exactly original, it's just like every other sun out there, and if our sun radiates microwaves, then it's very logical to assume that every other sun out there does so too.

(you just tried to lick your elbow......)