Why do scientists believe the universe is still expanding? a
Distant objects shift in frequency toward RED on the electromagnetic spectrum, which tells us objects are moving away from us

b
Distant objects shift in frequency toward YELLOW on the electromagnetic spectrum, which tells us objects are moving away from us

c
Distant objects shift in frequency toward BLUE on the electromagnetic spectrum, which tells us objects are closer to us us

I can't give you the answer but: The exact size of the universe is unknown. Scientists believe the universe is still expanding outward. They believe this outward expansion is the result of a violent, powerful explosion that occurred about 13.7 billion years ago. This explosion is known as the Big Bang. By looking at an object's electromagnetic spectrum, scientists can determine if an object is moving away from Earth or towards Earth.

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the use of electrical signals that transit messages is know as