Welcome to the Flat Earth Society forum, Ex-Globe!
When light travels it expands in all directions, like a balloon inflating.
So the power of the light decreases greatly as it travels
The power per unit area decreases due to spreading, yes. The total power does not decrease due to spreading alone, but does by absorption; "empty space" contains little that will absorb light and similar electromagnetic radiation.
Official source here:
https://van.physics.illinois.edu/qa/listing.php?id=21368
Read the third paragraph, he talks about light expanding and getting weaker.
It seems unlikely that light would be able to travel billions of miles without getting too weak to detect.
It depends on its intrinsic brightness (how strong it is to start with).
The scientist says lights power decreases by the distance travelled squared,is that an exponential decrease?
No. That is in
inverse square decrease; it is of the form 1/distance
2.
An exponential decrease with distance would be of the form 1/(some factor)
(some other factor) X distance.
That's why it takes larger telescopes to see dimmer objects. A telescope will collect four times as many photons as one with half the aperture, so, in principle, it takes a telescope twice as large in diameter to see a point source twice as far away as brightly, all else being equal (intrinsic brightness, absorption, etc.).
The same thing applies to any wave.
You need a huge transmitter just to get a radio signal to broadcast over several miles.
Not true. It's possible to communicate around the globe
using milliwatts of transmitted power, sometimes a lot less.
Just thinking about our sun, we are really close to our sun compared to a distant Star but our sun can only heat us up to about 120 degree Fahrenheit which isn't much compared to how hot it is really.
The Earth just intercepts a tiny fraction of the solar radiation; the cross section of the Earth is about 50,000,000 square miles (50 million). A sphere the radius of the Earth's orbit is 109,000,000,000,000,000 square miles (109 quadrillion) surface area, so only about .045 millionths of one percent of solar radiation is intercepted by the Earth. Of that, about half the energy reaching the top of the atmosphere is reflected or absorbed and re-radiated back into space by the atmosphere.