Photo: flickr
One thing that people might not be aware of is that we do not directly sense hard reality. What we see, hear, touch or taste is all filtered through our brains, which produces our perceptions in everyday life. And these brain simulations may or may not link up with reality! Take color perception for example. A person with colorblindness has always perceived grass as grey. His perception leads to his belief that all grass is grey, but actually, his senses cannot fully grasp reality.
When Sean Spicer, the press secretary of the White House, delivered a speech saying that Trump's inauguration was the largest seen in history, that statement is false (Ronald Reegan, the 40th president of the United States, holds that record if you really wanted to know). However, when questioned, another spokesperson said that the statement is an 'alternative fact'. Neuroscientists Susana Martinez-Conde and Stephen L. Macknik disagree on that term. They give a few pointers to address that, even though people may never directly experience reality, there is a way of measuring objective reality and obtaining unbiased knowledge.
One pointer, based on the scientific method, is that we can't ascertain something is true, but only that it is false. That is, our reality is only "true" until we learn something new about the world. That means that "truth" is constantly changing when something can prove it to be false. For example, Pluto, discovered in 1930, was originally thought to be a planet. However, new information and hot debates in the past fifteen years have changed that. In regards to Trump's inauguration, Spicer put out the claim that it drew the largest crowd in history. That can remain "true" until there is information to dispute it. And there is. Based on other sources, such as aerial photographs and public transit riders numbers, Spicer's statement has been disproven. "Alternative facts" are simply not facts.
Source material from Scientific American