Scientific Perspectives And Facts

I find it very helpful in trying to understand the world and the universe to express things in a scale that we can relate to. This is very helpful in gaining a sense of perspective on those areas that are out of the realm of our everyday experience.

Everyone is familiar with the typical highway driving speed of 100 kilometers per hour or about 65 miles per hour. Let's use this to build a sense of perspective on astronomical distances. If there was a road that circled the earth with no diversions and we drove night and day non-stop, we could circle the earth in about 16 days.

Now suppose the car was a very special car that could drive right up into the sky and continue into outer space, all at the usual highway speed and driving non-stop day and night.

We could drive to the moon in 153 days.

The two closest planets to earth are Venus, going toward the sun, and Mars, moving away from the sun. We could drive to Venus in 45 years and Mars in 84 years. Beyond Mars lies Jupiter, which would require 685 years.

It would take 163 years to drive to the sun and if a highway could be built on the sun's surface, it would take five and a half years to circle the sun.

The planet with the well-known ring system around it is Saturn. If we could drive around the outer edge of Saturn's rings, it would take about a year to make a complete circuit.

To drive to the edge of our Solar System, around the orbits of Neptune and Pluto, would take 3,500 years.

To drive to the nearest star, about 4 light-years distant, would require about 42 million years.

The earth is probably about 5,000 million years old. If we had started driving at that time, we would only have gotten about 79 light-years into space by now. This is about as far as the stars in the Big Dipper, which are relatively close by.

Distances in inter-stellar space are measured in light-years. A light-year is the distance that light travels in one years, about 6 trillion miles. A trillion is a million million. To drive a light-year at highway speeds would require more than ten million years. Our galaxy is about 100,00 light-years in diameter and we are about 30,000 light-years from the center. A neighboring Galaxy about the size of our galaxy is the Andromeda Galaxy, it is about a million light-years distant. So, we have a long ride ahead.

The universe is a big place. There are thousands of millions of times as many stars in the universe as there are grains of sand on earth.

Now, let's go to the opposite end of the scale and have a look at the atomic level.

Hydrogen is the lightest element with the smallest atoms. If we could line up 100 hydrogen atoms, that is about the length that a human hair grows in one second. The pages of a book are about two million atoms thick.

If a drop of water could be expanded so that it was as big as the entire earth, the atoms in the drop would be about the size of oranges. If we had as many strawberries as there are atoms in a drop of water, they would cover the earth's surface with a layer about 20 meters thick.

The vast majority of an atom is empty space. The nucleus takes up only about a trillionth of the volume of an atom, the rest is the space in which the electrons orbit the nucleus. If the atom could be compared to a large sports stadium, the nucleus would be a strawberry in the middle of the playing field. But the nucleus is so dense that if one were the size of a strawberry, it would weigh about 75 million tons.

Atoms that compose matter are so empty yet the reason one object placed atop another will not merge into it is that the negatively-charged electrons in each repel each other.

The electrons that orbit the nucleus in an atom are infinitesimal point particles with essentially no volume whatsoever. I read somewhere one of the most useful perspectives of all: an electron is proportional to the size of a mountain as the mountain is to the size of the entire universe. Thus, a mountain could be described as the midway point in scale between the near-infinite and the near-infinitesimal.

The total number of atoms in the universe is probably about 1 followed by 79 zeros. Although it is not apparent on earth, about 75% of all atoms are hydrogen.

Matter in the universe is extremely sparse relative to space. The estimated concentration of matter in space across the universe is estimated to be only about three hydrogen atoms per cubic meter. But this includes the vast reaches of nearly-empty inter-galactic space between galaxies. The galaxies across the universe are about a million times as dense in matter as the sorrounding inter-galactic space.

Despite the nuclear infernos of stars, the universe is an extremely cold place. It's average temperature is about 3 degrees Kelvin. That is, three Celsius degrees above absolute zero. This is the temperature at which all molecular motion stops and it is impossible to get any colder. Absolute zero is -273.16 degrees Celsius or -459 degrees Fahrenheit.

Gravity is the force that drives the universe on a large scale simply because it is cumulative. It is actually a very weak force. Two ocean liners docked side-by-side would have only about one pound of gravity between them.

It is important to remember that while our galaxy is aligned mostly along one geometric plane, except for the central bulge, and the orbits of the planets in our Solar System are also mostly aligned along one plane, these two planes are not the same. The plane of the planetary orbits in the Solar System is tilted about 60 degrees to the plane of the galaxy. When we look at the southern stars of the northern hemisphere summer, we are looking toward the center of the galaxy.

When you look at a half moon, which means that you see a quarter of it's total surface, you are looking at an area that is about the size of the U.S. or Canada or, China. When you see the full moon, which is half it's total area, you can see an area about the size of Russia.

In an incredible cosmic coincidence involving the size of the moon and it's distance from earth as well as the angular diameter of the sun, the shadow of the moon just reaches to the earth. The sun is about 400 times the diameter of the moon but is also about 400 times as distant. This is why solar eclipses occur only over a limited area on earth. I have seen many lunar eclipses but never a solar eclipse. A solar eclipse is where the moon casts it's shadow on the earth and a lunar eclipse is where the earth casts it's shadow on the moon. There is not an eclipse every time the moon orbits the earth because there is about 5 degrees difference between the plane of the earth's orbit around the sun and the plane of the moon's orbit around the earth.

The sun converts about four million tons of mass into energy every second and the earth receives about one part in two thousand million of this energy.

The earth is only a speck even in our own Solar System. The sun takes up about 99.86% of the mass of the Solar System and of that remaining, Jupiter is larger than all of the other planets combined.

If you think weather conditions are sometimes hostile on earth, Jupiter has atmospheric pressure about 200,000 times that of earth. Neptune has winds so powerful that they are like the shock waves from nuclear bombs would be in earth's atmosphere. Venus has dense clouds about 15 km thick so that only about 1% of the sunlight reaches the planet's surface. The clouds of Venus contain sulfuric acid so, if we brought an aluminum airplane there, it would disintegrate.


The average depth of the oceans on earth is 3600 meters. The average height of land above sea level is 760 meters. If the earth was a ball and you held it, the oceans would be so thin that you could not tell they were there. Only 1% of earth's water is available to us as fresh water.

The earth's atmosphere extends upward for hundreds of kilometers. But 75% of the air is in the troposphere below 11 km altitude.

We think of oxygen as a gas in the air but rocks also contain a vast amount of oxygen, combined with silicon plus many impurities.

Weather revolves around the simple fact that water is lighter than air by molecule so that it evaporates but when water molecules join together in large numbers by hydrogen bonding, it becomes 800 times as heavy as air at sea level so that it falls as precipitation.

Air is heavier than most people think. Pressurizing the cabin of a jet airliner might add a ton to it's weight. On the moon, a feather and a rock will fall at the same rate because there is no air resistance. If there were no air resistance to falling objects on earth, raindrops would be like bullets.

You probably have an atom in your body that was once a part of the body of anyone who has ever lived as long as they have been dead for a century or so.

Trees literally appear out of thin air. They take nutrients and water from the ground but their structure is composed of carbon taken from carbon dixoide in the air.

More than 90% of all species that have ever lived are now extinct.

There are about a million insects per person in the world and at any given time, you have about as many microscopic creatures on your body as there are people on earth.

A human being has undergone about half of their total intellectual development by the age of four.

By far the most important food in the world as a whole is rice. No other food even comes close.

If you want a vivid depiction of the population explosion, consider that humans have been on earth for maybe a million years but about one in every nine people that has ever lived is alive now.