The Persistent Myth of "Power"

It'll be a situation familiar to any amateur astronomer who participates in a lot of public outreach. A member of the general public will be ogling your enormous (to them), fancy (to them) telescope, and the inevitable question comes up.

"How powerful is it?"

You check to see what eyepiece is in the drawtube, and reply. In one recent instance, the answer was 37x when using a low power Plössl to observe the Perseus Double Cluster with my 8" dobsonian. The visitor seemed almost upset about this. "That's IT? With a telescope THIS BIG?" Unfortunately, his reaction isn't at all surprising, and we have low-end telescope manufacturers and cognitive biases to thank for that.

For most of the general public, the word "telescope" calls to mind the image of small refractors on spindly tripods that are seen in malls and department stores around Christmas time, usually advertising a magnification in the range of 575x. 

What people fail to understand is that this is unscrupulous advertising at its worst. On the surface of the deception is that 575x magnification is shockingly unrealistic in all but the highest-end, large aperture telescopes under the most pristine of observing conditions. Probing deeper, this fancy packaging plants in people's minds the most common misconception that exists about telescopes; that the purpose of a telescope is to magnify distant objects.

This is, of course, a natural assumption because telescopes always magnify the image being observed, but the truth is that magnification is essentially a byproduct of the telescope's primary purpose; to collect and focus light.

This seems counterintuitive to many until you compare a telescope collecting photons to a bucket collecting rain. If you have a bigger, wider bucket, you'll collect more rain. Telescopes work the same way, and it is, in fact, their primary purpose. With larger aperture optics, you will see brighter images with greater resolution. In fact, many amateur astronomers refer to large reflecting telescopes as "light buckets."

What surprises many people is that magnification isn't intrinsically defined by the telescope itself. The telescope's size and quality will dictate an upper limit of useful magnification under perfect seeing conditions, and the telescope's focal length will indicate what magnification you'll get with a specific eyepiece, but swapping eyepieces is what gives you different magnifications. The trick is to learn how to use the right magnification based on observing conditions and the object being observed.

Here we get to another misconception the public has about telescopes; that higher magnification gives a better view. In 95% of targets, the opposite is the case. Typically, astronomers reserve higher magnification for planets and double stars. The vast majority of observable objects in the sky are so large and so dim that high magnification can render them invisible, or only show you a small portion of the object. Take the Andromeda galaxy for example. The angular size of the object in our sky is so huge that most large telescopes can't frame the entire object in the field of view even when using the lowest practical magnification. Increasing the magnification also dims the view, which can be counterproductive when looking at "faint fuzzies."

It's always surprises people when you tell them that most serious deep sky observers actually go out of their way to be able to use the lowest magnification realistically possible with their telescopes. That is, at least. until you explain the bucket metaphor to them. Using a high power eyepiece with a big light bucket on a dim, diffuse object is like trying to bail out a large bucket full of rain water using a plastic coffee stirrer as a straw, while using a low power eyepiece is like bailing it out with a high-capacity pump.

Beyond being a shining example of how hype-filled marketing can give people a poor understanding of science (and make the job of science outreach more difficult), the magnification myth also serves as an illustration of how scientific fact is often at odds with what most people see as common sense. The truth is that our cognitive biases serve a purpose to us from an evolutionary standpoint. They help us organize the world into what makes sense and what doesn't based on the limited information provided by our senses and perception. This allows us to go about our daily lives without getting bogged down by sensory overload. Reality, however, is much more subtle and complex than the seemingly simple simulacrum filtered through our sensory restrictions and cognitive limitations. When our common sense breaks down under new contradictory data, the scientific method gives us a way of expanding the reach of our knowledge beyond what our senses and biases limit us to.

The real universe is far grander than the one our perception limits us to. To get the big picture, we must learn to use the right magnification.

The Intrinsic Knowability of the Past

Among the general population, and especially in the United States, scientific theories concerning how things were in the past such as the theories of evolution and the big bang are politically controversial. I say politically controversial, because there is no scientific controversy whatsoever. Unfortunately, there are many political and religious leaders who go to great lengths to deceive the populace as to the real workings of science with disastrous consequences. Feeble rhetorical devices like asking “were you there?” get parroted by individuals whose deep ideologies line up with the deceivers. The “were you there” question is ultimately one of the most insidious arguments by science deniers, but also one of the most fallacious. It is built around the idea that without a direct account by human narrators, the past is fundamentally unknowable.

Unfortunately, as exemplified by fraudsters, perjurers, and people who mistake the planet Venus for an alien spacecraft, human beings are notoriously unreliable narrators. One only needs to look at the “satanic abuse” moral panic of the 80's and 90's to see that people don't have to be deliberately deceitful in order to provide accounts that are 100% baloney. Additionally, the concept of human narrators being the only way to know the past is undermined by the laws of physics themselves. In fact, the past being knowable is a fundamental attribute of the universe we live in.

In general, there are three principles that ensure that at least a partial record of past natural events and phenomena is recorded, and those are the Laws of Conservation of Mass and Energy, the natural laws governing radioactive decay, and the finite speed of light being a cosmic speed limit.

First of all, matter is energy, and energy can not be created or destroyed. Mass can not be fully converted to other forms of energy, except through nuclear processes. This means that in general, objects that existed in the past often leave a record that they were there. Geological events don't rewrite the records laid down by prior ones, so stratigraphy can be used to read the life story of the earth. A plant or animal may be dead for millions of years, and while its remains may undergo a chemical change and petrify, the remains still exist leaving a record of their past presence on the planet. The moon may not be in its original material form, but by studying its orbit and composition, we understand that all of the material that makes up the moon was once a part of the earth before a cataclysmic collision between worlds ejected the matter that would one day accrete to form our natural satellite. Likewise, a record of the age of all of these things is knowable due to to the constants of radioactive decay.

Fossilized remains of Tyrannosaurus - photo from Wikipedia

The finite and unchanging speed of light means that we have a perpetual visual record of the past. When we observe distant corners of the universe through telescopes, we look into the distant past as well. We can see galaxies and stars dating back to the earliest generations when light first began to propagate through space. When looking at the Andromeda galaxy through a backyard telescope, we are looking directly at the time when wooly mammoths and glyptodonts roamed the grasslands of the desert southwest during the ice age. By observing galactic spectra, we can measure the rate of universal expansion and even see how quickly that expansion is accelerating. From there we can see how long ago the universe itself began.

The Andromeda Galaxy (M31) - Photo from Wikipedia

These key thing to understand is that these principles were not imagined by mankind; they were discovered. They are fundamental truths that were waiting to be found. We are slave to them, as they govern everything in our experience. No amount of wishful thinking can change the fact that these principles provide an objective record of the nature of the past.

People may not be reliable narrators, but if there's one thing science has taught us it's that the universe itself is, and we must be willing to listen to the stories it has to tell us.