By Don Lincoln, Ph.D., Fermi National Accelerator Laboratory
In 1964, two American astronomers, Arno Penzias and Robert Wilson were working for Bell Lab. They were studying the sources of radio waves in the Milky Way by employing a powerful antenna. Saggitarius-A, which happens to be a black hole in our galaxy is one of the powerful sources of these radio waves, but the two astronomers didn’t know about it. What happened next? Did the two astronomers discover something about the universe?
The Penzias and Wilson Experiment
Some energy is released in every explosion and the release of energy makes the things hot. With the passage of time the explosion expands and cools down. So, if the universe began with a bang, we should be able to see its afterglow and measure its temperature. But the interesting thing is that the research done into what is now known as black holes gave a deeper understanding of the start of the universe.
In any case, to do their work, Penzias and Wilson required a very accurate measurement. This means they had to have a thorough understanding of their telescope. So they started their telescope and checked if it could see radio sources like the Sun. For the purpose of confirming that they had not missed anything, they pointed their telescope at an empty spot in the sky.
Seen in this context, empty here means that there were no astronomical bodies at that spot. Their expectation was that there would be no radio waves there. But when they actually pointed their telescope at the empty spot, they heard a hiss in their receiver. They did not understand what kind of sound it was. In fact, it could be anything.
They cross-checked their amplifiers, electrical grounds, and whatever possible reasons that could have caused that sound. But even after that, the radio hiss was still there. They then found out that the radio antenna was full of bird poop. So, they cleaned that out too. The hiss still did not go away.
Then, they tried to point their telescope in many different directions making sure all of them were empty. They found the same radio hiss everywhere. This meant that the hiss was there because either their instrument was not functioning properly or there was something here on the Earth.
This is a transcript from the video series Understanding the Misconceptions of Science. Watch it now, on The Great Courses Plus.
The Discovery of the Radio Hiss
After thinking for some time and discussing with some of their colleagues, they realized that they were detecting a hiss because the universe is full of radio hiss. The thing they had discovered was real and not because of the malfunctioning or effect of the instrument. It emerged that the whole universe was releasing a uniform set of radio waves that they could catch as radio hiss on their receiver.
This is what you would precisely expect in case the big bang theory is correct. That radio hiss is in fact, the afterglow of the initial explosion. And maybe, some temperature can be assigned to what they were seeing. The radio waves observed by them were precisely what could be expected if the universe was –455° Fahrenheit, –270° Centigrade, or 2.7° Kelvin. The universe is very cold. One more interesting aspect was that the radio hiss was amazingly uniform which means that the temperature is also remarkably uniform. So, at the deepest level, our way of thinking about gravity is completely changed with Einstein’s theory of special relativity.
Learn more about where exactly mass comes from.
Einstein’s Theory of General Relativity
Unlike a force that we know more of, meaning gravity is a force that pulls downward, gravity is in fact, a bending of the space. Huge objects like the Earth and the Sun distort the space very much. And when you bend the space, you can make objects move in curved paths. For example, the Earth orbiting the Sun. Now, this is an idea that can confuse the brain. It may take some time to understand it. Einstein’s theory has been tested countless times. If you’re a mathematically minded person, you can write Einstein’s basic equations to highlight a specific meaning. Space and time is simply equal to a constant times energy and mass.
Let’s assume that you are willing to accept this idea, we can apply it to big bang also. The theory of general relativity says that before the start of the expansion of the universe, the whole matter and energy of the universe was concentrated in a single spot that was a sphere with zero size. In science, it is called a singularity.
Now, let’s join these two ideas. If whole mass and energy were situated in a single point and mass and energy are equal to space and time times a constant then it would mean that space and time should also be in a single space. That in tune means, there is only one space. It is not that there is a space and there is a singularity in that space and then it explodes. It is much weirder than that.
The thing is that the whole space exists inside that point. Everything exists inside that point. And if everything is inside that point then it is clear there is nothing outside that point. That means at the time of occurrence of the big bang, the explosion did not expand into space.
It further means that space was created during the expansion. And it literally means there was nothing outside the universe. And if the whole space was inside just a single point then it means that all the points that we exist in and are familiar with were at the center. This means all locations in the universe can claim to be the center of the universe. And this is a mind-boggling concept.
Learn more about how relativity is misunderstood.
Common Questions about Radio Hiss, Einstein’s Theory of Relativity, and the Universe
Radio hiss was discovered by Arno Penzias and Robert Wilson in 1964.
Arno Penzias and Robert Wilson discovered that the whole universe was releasing a uniform set of radio waves. This is what they were able to catch as radio hiss on their receiver.
Einstein’s theory of general relativity states that before the start of the expansion of the universe, the whole matter and energy of the universe was concentrated in a single spot that was a sphere with zero size.
