Three Theories Regarding the Expansion of the Universe

Robert: College Student: The Expansion of the Universe

Orlav began his lesson: “As we studied before, Einstein said that closer to speed of light something travels, the more massive it becomes. 'Big Bang' was explosion that created our universe. What does tell you about beginning of universe?” Orlav scanned the audience. “John?” He knew this student's name because he was hard to forget – unruly hair, ragged clothing … and exceptionally intelligent.

“I'm guessing that the Big Bang must have been a very fast explosion. Sorry,” he chuckled, “I know that sounds moronic. What I mean is that the explosion must have happened at nearly the speed of light?”

“Da, explosion extremely powerful,” Orlav agreed. “Occurred out at velocity very close to light speed,” the professor confirmed, nodding his head and miming an expanding circle with his hands. “How does high speed affect mass? From super-fast explosion?”

John acknowledged, “It would make the Big Bang infinitely massive because it's so near the speed of light. Lots of force packed in there.”

Orlav forged on, “It flows outwards at very, very high speed, fastest at the beginning. What tells you about Time?”

John offered, “Doesn't Time slow the closer an object is to traveling at light speed? So,” he hesitated, “wouldn't Time barely be going?” He fumbled. “Or at least be occurring very slowly at the initial explosion?”

Nodding, but not answering directly, the professor switched tactics by asking the group, “Did any of you read materials for this week?” Most nodded, a few uncertainly. “Who to explain Friedman's three theories about beginning of universe?”

A student named Sarah eagerly waved her hand. Professor Orlav motioned to her. She stood up, unnecessarily. “Freidman believed that the Universe is doing one of three things,” she announced importantly. She ticked her points of on her fingers, one by one.

1) The universe is 'exploding' outwards but will eventually lose “steam” and will again collapse on itself

2) The expansion began to slow for awhile but eventually overcame the “drag” of gravity and will never rein itself back in again. It’s expanding faster now.

3) The universe has attained 'escape velocity' and won't collapse, but its expansion is still gradually slowing down over time.

“Ochen khahrahshoh, Sarah.” She nodded happily oblivious to the many students who rolled their eyes behind her back.

“I, like many scientists believe #2 is correct: The universe was expanding, slower at the middle stages and faster later. Never slow at the beginning,” he emphasized. Let me ask again: If outward expansion was greatest at start of explosion – how would Time appear?”

Sarah replied, “Well, like John said, if the universe started by exploding at nearly light speed, Time would be very slow at the beginning.”

Continuing he said, “Whichever of three theories you believe, Time had a definite start. Time has not always been, even though you may have thought so. For our reality, time and mass started then too.” The professor was really getting into his element now. He drew in a big breath and raised his voice, “Now, think this.” He drew a circle on the board with a 'Big Bang' in the center. He drew another ring around the outside of the first like water rings on a pond. He drew multiple arrows pointing outward from 'Big Bang'. He put an 'X' on one of the inner rings.

“If you are here,” he clarified, pointing to the X', “and you are near beginning of universe that moves out at two-thirds the speed of light, would you say that planet on other side opposite of you expands out at same speed?” The students nodded their heads. No debate there.

“So, if you move out at two-thirds the speed of light, and other person on other opposite side travels out at same speed, would you have,” he searched for the right word, “'spreading' speed at velocity greater than light speed?” Most nodded in confirmation. “In effect, da. Light from other side never reach you. Think that you may never even know about other side of universe no matter how good is your telescope. Do you understand?” He peered at them, his walrus mustache twitching impatiently. “Neither one moves out faster than speed of light, but 'spreading' effect does. Any 'part' of universe that expands at more than 50% of light-speed will never see other half also moving away at more than half light-speed.” He slapped his hands together like he was dusting them off … and as if he'd just explained the most obvious of facts to them.