[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-detail-40809-en":3,"doc-seo-40809-105":30,"detail-sidebar-cat-0-en-105":91},{"code":4,"msg":5,"data":6},0,"success",{"doc_id":7,"user_id":8,"nickname":9,"user_avatar":10,"doc_module":4,"category_id":11,"category_name":12,"doc_title":13,"doc_description":14,"doc_content":15,"file_id":16,"file_url":17,"file_type":18,"file_size":19,"view_count":20,"is_deleted":4,"is_public":21,"is_downloadable":21,"audit_status":21,"page_count":22,"language":23,"language_code":24,"site_id":25,"html_lang":24,"table_of_contents":26,"faqs":27,"seo_title":13,"seo_description":14,"update_tm":28,"read_time":29},40809,1374391974468,"Eden","https://ap-avatar.wpscdn.com/davatar_29158cc5080c5b710cf443261637dec0",8,"Research & Report","Stephen Hawking The Nature of Space and Time","A set of technical lecture remarks by Stephen Hawking on the nature of space and time, presented alongside Roger Penrose’s contrasting viewpoints. Hawking emphasizes the use of general relativity and quantum theory, discusses differences in approaches to quantum gravity, and defends a positivist view of physical theories. He argues for the continued success of continuum spacetime theories, critiques string theory’s lack of testable predictions, and outlines how gravity’s distinctive role yields ideas such as beginnings of spacetime and intrinsic gravitational entropy.","hep-th/ 9409 195 30 Sep 94  \n1. Classical Theory  \nS. W. Hawking  \nIn these lectures Roger Penrose and I will put forward our related but rather di􀀋erent viewpoints on the nature of space and time. We shall speak alternately and shall give three lectures each, followed by a discussion on our di􀀋erent approaches. I should emphasize that these will be technical lectures. We shall assume a basic knowledge of general relativity and quantum theory.  \nThere is a short article by Richard Feynman describing his experiences at a conference on general relativity. I think it was the Warsaw conference in 1962 . It commented very unfavorably on the general competence of the people there and the relevance of what they were doing. That general relativity soon acquired a much better reputation, and more interest, is in a considerable measure because of Roger's work. Up to then, general relativity had been formulated as a messy set of partial di􀀋erential equations in a single coordinate system. People were so pleased when they found a solution that they didn't care that it probably had no physical signi􀀌cance. However, Roger brought in modern concepts like spinors and global methods. He was the 􀀌rst to show that one could discover general properties without solving the equations exactly. It was his 􀀌rst singularity theorem that introduced me to the study of causal structure and inspired my classical work on singularities and black holes.  \nI think Roger and I pretty much agree on the classical work. However, we di􀀋er in our approach to quantum gravity and indeed to quantum theory itself. Although I'm regarded as a dangerous radical by particle physicists for proposing that there may be loss of quantum coherence I'm de􀀌nitely a conservative compared to Roger. I take the positivist viewpoint that a physical theory is just a mathematical model and that it is meaningless to ask whether it corresponds to reality. All that one can ask is that its predictions should be in agreement with observation. I think Roger is a Platonist at heart but he must answer for himself.  \nAlthough there have been suggestions that spacetime may have a discrete structure I see no reason to abandon the continuum theories that have been so successful. General relativity is a beautiful theory that agrees with every observation that has been made. It may require modi􀀌cations on the Planck scale but I don't think that will a􀀋ect many of the predictions that can be obtained from it. It may be only a low energy approximation to some more fundemental theory, like string theory, but I think string theory has been over sold. First of all, it is not clear that general relativity, when combined with various other 􀀌elds in a supergravity theory, can not give a sensible quantum theory. Reports of  \nthe death of supergravity are exaggerations. One year everyone believed that supergravity was 􀀌nite. The next year the fashion changed and everyone said that supergravity was bound to have divergences even though none had actually been found. My second reason for not discussing string theory is that it has not made any testable predictions. By contrast, the straight forward application of quantum theory to general relativity, which I will be talking about, has already made two testable predictions. One of these predictions, the development of small perturbations during in􀀍ation, seems to be con􀀌rmed by recent observations of 􀀍uctuations in the microwave background. The other prediction, that black holes should radiate thermally, is testable in principle. All we have to do is 􀀌nd a primordial black hole. Unfortunately, there don't seem many around in this neck of the woods. If there had been we would know how to quantize gravity.  \nNeither of these predictions will be changed even if string theory is the ultimate theory of nature. But string theory, at least at its current state of development, is quite incapable of making these predictions except by appealing to general relativity as the lo","cbCaif7nE0CfRBte","https://ap.wps.com/l/cbCaif7nE0CfRBte","pdf",370688,3,1,61,"English","en",105,"# Classical Theory\n## Viewpoints on space and time\n## Quantum gravity vs quantum theory\n## Continuum spacetime and string theory critique\n## Testable implications of quantum gravity\n## Gravity, spacetime structure, and gravitational entropy\n## Lecture roadmap","[{\"question\":\"What philosophical stance does Hawking take toward physical theories?\",\"answer\":\"Hawking adopts a positivist viewpoint: a physical theory is a mathematical model, and it is only meaningful insofar as its predictions agree with observation.\"},{\"question\":\"Why does Hawking argue against relying on string theory for these lectures?\",\"answer\":\"He cites string theory’s limited testable predictions and suggests it may not yield observational results beyond those already obtainable from general relativity or supergravity.\"},{\"question\":\"What two key testable ideas does Hawking mention from applying quantum theory to general relativity?\",\"answer\":\"He highlights (1) small perturbations during inflation and their confirmation via microwave background fluctuations, and (2) the thermal radiation of black holes, which is testable in principle if primordial black holes are found.\"}]",1783315289,154,{"code":4,"msg":31,"data":32},"ok",{"site_id":25,"language":24,"slug":33,"title":13,"keywords":34,"description":14,"schema_data":35,"social_meta":86,"head_meta":88,"extra_data":90,"updated_unix":28},"stephen-hawking-the-nature-of-space-and-time","",{"@graph":36,"@context":85},[37,53,68],{"@type":38,"itemListElement":39},"BreadcrumbList",[40,44,48,50],{"item":41,"name":42,"@type":43,"position":21},"https://docshare.wps.com","Home","ListItem",{"item":45,"name":46,"@type":43,"position":47},"https://docshare.wps.com/document/","Document",2,{"item":49,"name":12,"@type":43,"position":20},"https://docshare.wps.com/document/research-report/",{"item":51,"name":13,"@type":43,"position":52},"https://docshare.wps.com/document/stephen-hawking-the-nature-of-space-and-time/40809/",4,{"url":51,"name":13,"@type":54,"author":55,"headline":13,"publisher":57,"fileFormat":60,"inLanguage":24,"description":14,"dateModified":61,"datePublished":62,"encodingFormat":60,"isAccessibleForFree":63,"interactionStatistic":64},"DigitalDocument",{"name":9,"@type":56},"Person",{"url":41,"name":58,"@type":59},"DocShare","Organization","application/pdf","2026-07-13","2026-07-06",true,{"@type":65,"interactionType":66,"userInteractionCount":20},"InteractionCounter",{"@type":67},"ViewAction",{"@type":69,"mainEntity":70},"FAQPage",[71,77,81],{"name":72,"@type":73,"acceptedAnswer":74},"What philosophical stance does Hawking take toward physical theories?","Question",{"text":75,"@type":76},"Hawking adopts a positivist viewpoint: a physical theory is a mathematical model, and it is only meaningful insofar as its predictions agree with observation.","Answer",{"name":78,"@type":73,"acceptedAnswer":79},"Why does Hawking argue against relying on string theory for these lectures?",{"text":80,"@type":76},"He cites string theory’s limited testable predictions and suggests it may not yield observational results beyond those already obtainable from general relativity or supergravity.",{"name":82,"@type":73,"acceptedAnswer":83},"What two key testable ideas does Hawking mention from applying quantum theory to general relativity?",{"text":84,"@type":76},"He highlights (1) small perturbations during inflation and their confirmation via microwave background fluctuations, and (2) the thermal radiation of black holes, which is testable in principle if primordial black holes are 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