What exactly is space, anyway? Is it made of anything? Does it have an existence independent of the things that occupy it? If you take all of the matter out of the universe, would there be space that remains?
Space isn’t just the vast expanse beyond Earth’s atmosphere. Earth has space, as much as it occupies space. Though it’s a question that we may have never asked ourselves, many of history’s greatest scientists and philosophers have wondered about the nature of space.
Almost exactly 300 years ago, in 1717, the German-born British Queen Caroline of Ansbach ignited a debate that would last to the present day. English historian Lucy Worsley has called her “the cleverest queen consort ever to sit on the throne of England”. This glowing assessment of the Queen’s intellectual capabilities may have been well-deserved. Aside from being Queen, Caroline was also an avid philosopher who encouraged a healthy exchange of ideas between philosophers of different schools of thought.
Gottfried Leibniz (left) and Samuel Clarke (right)
Because of Caroline, two prominent philosophers of the era began an exchange of letters. The German rationalist Gottfried Leibniz and the English absolutist Samuel Clarke began writing each other at Caroline’s behest, and one of the biggest philosophical matters they tackled was the nature of space. The correspondence between the two was eventually collated and published as A Collection of Papers.
Leibniz and Clarke were unable to neatly settle the matter between themselves. According to Leibniz, space was the spatial relation between things. For example, the moon is 384,400 kilometers away from Earth. If all matter in the universe ceased to exist, so would space, because space is nothing but spatial relations between objects.
Clarke, meanwhile, argued that space is what contains all of us--you, me, other people, Earth, the Solar System, the universe. Because of space, we understand how all matter in the universe moves. Clarke also added that space is divine--that space is actually God, and thus, the disappearance of all matter would not precede the disappearance of space.
Of course, a debate of this nature wasn’t contained to all but two participants. Isaac Newton also waded into the foray, saying that objects move in relation to to other objects, like how the moon moves in relation to the Earth. However, objects also move absolutely, in relation to space.
It’s difficult to see which idea is heads and shoulders above the rest. Immanuel Kant, for example, thinks that space isn’t an entity in itself, but rather a concept--a tool--that humans use to understand the world better. Obviously, these different ideas all have their own merits. Thus, where is the debate now in the present time?
Is a hippo more divine than Newton?
If space is divine, then are objects that occupy larger spaces more divine than those that occupy smaller spaces? Is a hippopotamus, for example, more valuable than Sir Isaac Newton? Of course not, says Bertrand Russell, a 20th century philosopher. "Sir Isaac Newton was very much smaller than a hippopotamus, but we do not on that account value him less than the larger beast.” The dilemma of considering a large beast more divine than a smaller man, however, possibly had the potential of being a real philosophical issue among 18th century philosophers.
Because considering space to be divine leads to potentially hairy philosophical questions, more modern thinkers have shied away from the concept. However, aside from the part of divinity, Clarke’s ideas about the nature of space concur with contemporary ideas in physics. Other contemporary physicists, meanwhile, think that both Leibniz’s and Clarke’s theories can also fit well in modern physics.
As of now, therefore, we don’t have an actual definition of space. We can describe what the expanse of space is like beyond Earth, but we don’t really know what space itself is, exactly. Maybe it’ll take another three centuries of philosophical debate and scientific reasoning to find out.
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